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  <p class="align-right"><strong>built-in predicate</strong></p>
<section id="create-logtalk-flag-3">
<span id="predicates-create-logtalk-flag-3"></span><span id="index-0"></span><h1><code class="docutils literal notranslate"><span class="pre">create_logtalk_flag/3</span></code><a class="headerlink" href="#create-logtalk-flag-3" title="Link to this heading"></a></h1>
<section id="description">
<h2>Description<a class="headerlink" href="#description" title="Link to this heading"></a></h2>
<div class="highlight-logtalk notranslate"><div class="highlight"><pre><span></span><span class="k">create_logtalk_flag</span>(<span class="nv">Flag</span>, <span class="nv">Value</span>, <span class="nv">Options</span>)
</pre></div>
</div>
<p>Creates a new Logtalk flag and sets its default value. User-defined
flags can be queried and set in the same way as predefined flags by
using, respectively, the <a class="reference internal" href="current_logtalk_flag_2.html#predicates-current-logtalk-flag-2"><span class="std std-ref">current_logtalk_flag/2</span></a> and
<a class="reference internal" href="set_logtalk_flag_2.html#predicates-set-logtalk-flag-2"><span class="std std-ref">set_logtalk_flag/2</span></a> built-in predicates. For a
description of the predefined compiler flags, please see the
<a class="reference internal" href="../../userman/programming.html#programming-flags"><span class="std std-ref">Compiler flags</span></a> section in the User Manual.</p>
<p>This predicate is based on the specification of the SWI-Prolog
<code class="docutils literal notranslate"><span class="pre">create_prolog_flag/3</span></code> built-in predicate and supports the same
options: <code class="docutils literal notranslate"><span class="pre">access(Access)</span></code>, where <code class="docutils literal notranslate"><span class="pre">Access</span></code> can be either
<code class="docutils literal notranslate"><span class="pre">read_write</span></code> (the default) or <code class="docutils literal notranslate"><span class="pre">read_only</span></code>; <code class="docutils literal notranslate"><span class="pre">keep(Keep)</span></code>, where
<code class="docutils literal notranslate"><span class="pre">Keep</span></code> can be either <code class="docutils literal notranslate"><span class="pre">false</span></code> (the default) or <code class="docutils literal notranslate"><span class="pre">true</span></code>, for deciding
if an existing definition of the flag should be kept or replaced by the
new one; and <code class="docutils literal notranslate"><span class="pre">type(Type)</span></code> for specifying the type of the flag, which
can be <code class="docutils literal notranslate"><span class="pre">boolean</span></code>, <code class="docutils literal notranslate"><span class="pre">atom</span></code>, <code class="docutils literal notranslate"><span class="pre">integer</span></code>, <code class="docutils literal notranslate"><span class="pre">float</span></code>, or <code class="docutils literal notranslate"><span class="pre">term</span></code> (which
only restricts the flag value to ground terms). When the <code class="docutils literal notranslate"><span class="pre">type/1</span></code>
option is not specified, the type of the flag is inferred from its
initial value.</p>
</section>
<section id="modes-and-number-of-proofs">
<h2>Modes and number of proofs<a class="headerlink" href="#modes-and-number-of-proofs" title="Link to this heading"></a></h2>
<div class="highlight-logtalk notranslate"><div class="highlight"><pre><span></span><span class="k">create_logtalk_flag</span>(<span class="o">+</span>atom, <span class="o">+</span>ground, <span class="o">+</span>list(ground)) <span class="o">-</span> one
</pre></div>
</div>
</section>
<section id="errors">
<h2>Errors<a class="headerlink" href="#errors" title="Link to this heading"></a></h2>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">Flag</span></code> is a variable:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">instantiation_error</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Value</span></code> is not a ground term:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">instantiation_error</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Options</span></code> is not a ground term:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">instantiation_error</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Flag</span></code> is neither a variable nor an atom:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">type_error(atom,</span> <span class="pre">Flag)</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Options</span></code> is neither a variable nor a list:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">type_error(atom,</span> <span class="pre">Flag)</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Value</span></code> is not a valid value for flag Flag:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">domain_error(flag_value,</span> <span class="pre">Flag</span> <span class="pre">+</span> <span class="pre">Value)</span></code></div>
</div>
<div class="line"><code class="docutils literal notranslate"><span class="pre">Flag</span></code> is a system-defined flag:</div>
<div class="line-block">
<div class="line"><code class="docutils literal notranslate"><span class="pre">permission_error(modify,</span> <span class="pre">flag,</span> <span class="pre">Flag)</span></code></div>
</div>
<div class="line">An element <code class="docutils literal notranslate"><span class="pre">Option</span></code> of the list <code class="docutils literal notranslate"><span class="pre">Options</span></code> is not a valid option</div>
<div class="line-block">
<div class="line">domain_error(flag_option,Option)</div>
</div>
<div class="line">The list <code class="docutils literal notranslate"><span class="pre">Options</span></code> contains a <code class="docutils literal notranslate"><span class="pre">type(Type)</span></code> option and <code class="docutils literal notranslate"><span class="pre">Value</span></code> is not of type <code class="docutils literal notranslate"><span class="pre">Type</span></code></div>
<div class="line-block">
<div class="line">type_error(Type, Value)</div>
</div>
</div>
</section>
<section id="examples">
<h2>Examples<a class="headerlink" href="#examples" title="Link to this heading"></a></h2>
<div class="highlight-logtalk notranslate"><div class="highlight"><pre><span></span><span class="c">% create a new boolean flag with default value set to false:</span>
| <span class="o">?-</span> <span class="k">create_logtalk_flag</span>(pretty_print_blobs, <span class="k">false</span>, []).
</pre></div>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<p><a class="reference internal" href="current_logtalk_flag_2.html#predicates-current-logtalk-flag-2"><span class="std std-ref">current_logtalk_flag/2</span></a>,
<a class="reference internal" href="set_logtalk_flag_2.html#predicates-set-logtalk-flag-2"><span class="std std-ref">set_logtalk_flag/2</span></a></p>
</div>
</section>
</section>


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